Modulated Triangular Wave Amplifier

ABSTRACT

The invention is a power amplifier circuit for providing a signal acceptable for use in audio amplifiers or similar applications without requiring a stable power supply free from fluctuations. An alternating current power supply signal rectified to a direct current signal is processed by two voltage multipliers. A voltage divider establishes a unity gain level, and the variance from this voltage is squared by the first voltage multiplier. This squared voltage is then multiplied with a triangular wave signal to generate a modulated triangular wave signal. The modulated triangular wave signal and a signal to be amplified, typically an audio signal, are processed by an internal comparator to generate a pulse width modulated signal. This modulated signal is processed by a power transistor network and filter to provide an amplified signal to a load device. By modulating the triangle wave signal to compensate for fluctuations in the power supply to the amplifier circuit, noise or ripples present in the power supply are demodulated, eliminating the requirement for a regulated power supply.

TECHNICAL FIELD OF INVENTION

The present invention relates to amplifier design, and more particularlyto a power amplifier for audio and other signals. Still morespecifically, the present invention relates to design of an amplifiercircuit capable of manipulating an unregulated AC signal to provide anamplified signal to a load device, so that fluctuations in the powersupply to the amplifier circuit are compensated for, and noise orripples present in the power supply are removed, eliminating therequirement for a regulated power supply.

BACKGROUND OF THE INVENTION

Power amplifiers are commonly used to amplify electrical signalssupplying power to certain types of electronic devices, such as audiospeakers. Most power amplifiers use, and depend upon, clean, regulateddirect current (DC) power input. Unregulated DC power generated fromunregulated alternating current (AC) is “noisy”, containing powerfluctuations unsuitable for most power amplifying applications.

In typical applications, power amplifiers must convert an unregulated,noisy 120-volt AC power source into a regulated, clean DC power source.If the unregulated AC power input is simply rectified to a DC powerinput, any fluctuations, noise or ripple in the AC power signal may betransferred to the DC power signal. The noise inherent in DC power inthis situation may be translated to the amplified output signal. Inaudio applications, such excessive variances in the power supply willresult in undesirable hum, distortions, and noise at the speaker. Assuch, there is a need for regulated DC power supplies to powerapplications with a reduced noise factor.

Conventional power amplifiers rectify an AC signal to a regulated DCpower source with transformers and other active inductive and capacitivecircuits, which account for the majority of the weight, waste heatoutput, and cost of production associated with these prior-artamplifiers. As such, there is also a need for audio amplifiers thatweigh less, produce less heat, and cost less.

A number of approaches have been tried to minimize or overcome theabove-identified problems. U.S. Pat. No. 4,042,890 to Eckerie filtersthe DC power signal to reduce high-frequency noise. U.S. Pat. No.4,605,910 to Covill produces a switch modulated signal for producing anoutput signal that is independent of the supply voltage, therebyeliminating noise caused by fluctuating AC voltage signals. U.S. Pat.No. 4,737,731 to Swanson senses variations in the DC power signal andadjusts the gain in the audio frequency signal according to thevariances to reduce modulation distortion. In U.S. Pat. No. 5,132,637also to Swanson, a plurality of actuable power amplifiers are controlledby a correction signal to produce a cleaner signal. U.S. Pat. No.5,777,519 to Simopoulos uses a correction signal as an input to avariable switching power supply to eliminate some noise in the powersignal.

However, each of these methods share the problems of high cost, highheat loss, high weight, and overall inefficiency. A different method forregulating the power output that eliminates the regulated DC powersource would offer significant advantages in cost and efficiency as wellas a significant reduction in weight and increase in output power.

SUMMARY OF THE INVENTION

The present invention eliminates the need to regulate a DC power supplyby regulating the gain of an amplifier in response to fluctuations andripple in the unregulated DC power supply so that those fluctuations andripples do not appear at the output power signal. Unregulated AC powermay be supplied from a conventional AC outlet or from an isolation orother transformer. Unregulated AC power is first rectified intounregulated DC power, and this unregulated DC power signal is monitoredby a voltage divider to establish a power supply “variance” signal. Thisvariance signal is then squared by an analog multiplier. A secondmultiplier processes the signal from the first multiplier with atriangular wave signal to produce an input signal to an internalcomparator. The first and second voltage multipliers comprise atriangular wave modulator. The resulting output signal from the secondmultiplier is the modulated triangular wave signal.

An internal comparator accepts an input audio signal as well as theoutput signal from the second multiplier. This internal comparatormonitors and processes the input audio signal with the modulatedtriangular wave signal to generate a Pulse Width Modulation (PWM) outputsignal. From the internal comparator, the PWM output signal is amplifiedby power device transistors, and the amplified PWM signal passes throughfilters to remove a high-frequency carrier component. The signal outputfrom the filters is an amplified PWM power signal, which is then used todrive a load device.

The variances in the power supply voltage are demodulated or removed bythis approach, thereby eliminating the need for a regulated DC powersupply. The invention provides for dynamic adjustment for noise in theunregulated DC power supply, resulting in a simpler and more efficientpower amplifier to derive a clean, regulated, amplified power drivesignal. The present invention also provides audio improvements includingcompression and frequency equalization.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention will become more readilyunderstood from the following detailed description and appended claimswhen read in conjunction with the accompanying drawings in which likenumerals represent like elements.

FIG. 1 is a basic circuit block diagram illustrating a preferredembodiment of the functional components of the power amplifier of thepresent invention.

FIG. 2 is a circuit schematic of a preferred embodiment of the AC powercircuit.

FIG. 3 is the circuit schematic of a preferred embodiment of the DCbridge rectifier and voltage divider.

FIG. 4 is a circuit schematic of a preferred embodiment of thetriangular wave modulator (TWM) containing two voltage multipliers.

FIG. 5 is a circuit schematic of a preferred embodiment of the pulsewidth modulator (PWM) controller containing the triangular wavegenerator and pulse width modulation amplifier.

FIG. 6 is the circuit schematic of a preferred embodiment of the powerdevice transistor and filter.

FIG. 7 is a circuit schematic of a preferred embodiment of the RMS-to-DCconverter used to provide an additional signal for providing dynamicrange compression, or Automatic Gain Control, to the amplifier circuit.

FIG. 8 is a composite circuit schematic of a preferred embodiment of thepresent invention for a modulated triangular wave audio power amplifier.

FIG. 9 illustrates the internal operative connectivity for the PWMcontroller illustrated schematically and described in detail inconnection with FIG. 5.

FIG. 10 is a block diagram of the modulated triangular wave audio poweramplifier configured as a noise-canceling amplifier.

FIG. 11 is a block diagram of the modulated triangular wave audio poweramplifier configured to compress or expand dynamic range or for signalequalization or cancellation.

FIG. 12 is a block diagram of the modulated triangular wave audio poweramplifier configured to introduce an additional signal to output.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following Detailed Description of the Preferred Embodiments,reference is made to the accompanying drawings which form a part hereof,and in which are shown by way of illustration specific embodiments inwhich the invention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention. For example,intervening electrical components may be located along electricalconnections, and electrical components of different ratings may be used,without departing from the scope of the present invention. Moreover,persons of ordinary skill in the art will know that numerous minoralternatives to a specific circuit design are possible, withoutdeparting from the scope of the present invention. Thus understood, thedetails of the circuit provided, including the ratings of the electricalcomponents in the specific preferred embodiments, are not intended tolimit the scope of any claim, nor to be read into any claim, but merelyto provide an example of a fully enabled and disclosed best mode ofpracticing a preferred embodiment of the invention.

FIG. 1 illustrates a preferred embodiment of the basic electricalcomponents of the amplifier of the present invention. As seen in FIG. 1,an AC power supply 5 is coupled to an optional AC power circuit(transformer) 7 by an electrical connection 50. Optional AC powercircuit 7 is coupled to a bridge rectifier 10 by an electricalconnection 51. Bridge rectifier 10 is coupled to a voltage divider 15 byan electrical connection 55. Bridge rectifier 10 is also coupled to apower device transistor 30 by an electrical connection 60.

Voltage divider 15 is coupled to a first input 21 of a first voltagemultiplier 20 by an electrical connection 65 and to a second input 22 byan electrical connection 66. The output of first voltage multiplier 20is coupled to a first input 24 of a second voltage multiplier 23 by anelectrical connection 67. A triangular wave generator 27 is coupled to asecond input 26 of second voltage multiplier 23 by electrical connection68. First voltage multiplier 20 and second voltage multiplier 23comprise a triangular wave modulator (TWM) 91.

The output of second voltage multiplier 23 is coupled to a first input28 of an internal comparator 25 by an electrical connection 70. In apreferred embodiment, an audio signal source 35 is coupled to a secondinput 29 of an internal comparator 25 by an electrical connection 80.The output of internal comparator 25 is coupled to a power devicetransistor 30 by an electrical connection 75. In the preferredembodiment, internal comparator 25 is internal of a pulse widthmodulation controller integrated circuit (PWM controller 93) thatincludes triangular wave generator 27, as described in detail below.Power device transistor 30 is coupled to a filter 40 by an electricalconnection 85. Filter 40 is coupled to a load device 45 by an electricalconnection 90.

In operation, unregulated AC power supply 5 supplies an unregulated, ACpower signal to the amplifier. The unregulated AC power signal passesthrough bridge rectifier 10, which rectifies, or converts, theunregulated AC power signal into an unregulated DC power signal. Thisunregulated DC power signal is used to provide a reference voltage totriangle wave modulator 91 as well as being used by power devicetransistors 30 to power load device 45.

From bridge rectifier 10, the unregulated DC power signal passes throughvoltage divider 15. Voltage divider 15 establishes a unity voltage leveland provides two input power signals comprising the voltage variance ofthe power signal into first voltage multiplier 20. First voltagemultiplier 20 multiplies these two signals together, providing anunregulated DC power signal equal to the square of the voltage variance.

The output of first voltage multiplier 20 is coupled to first input 24of second voltage multiplier 23. Triangular wave generator 27 generatesa triangular wave signal that is coupled to second input 26 of secondvoltage multiplier 23. These two signals are multiplied together bysecond voltage multiplier 23 to generate a modulated triangular wavesignal.

The modulated triangular wave signal, output from triangular wavemodulator 91, is the first input to PWM Amp 25. The second input to PWMAmp 25 is the audio signal being amplified, from audio source 35. PWMAmp 25 compares the modulated triangular wave signal and the audiosignal to generate a pulse width modulation (PWM) power signal carryingthe audio component. The PWM power signal then passes to power devicetransistors 30, which amplify the PWM power signal. This amplified PWMpower signal then passes through filter 40 (e.g., an inductancecapacitor filter) which filters out the high-frequency carrier componentof the PWM power signal. This filtered PWM power signal provides aclean, undistorted audio signal free of noise to load device 45 becausethe modulated triangle wave signal compensates for variances in AC powersupply 5, powering the load device 45 for the relevant application.

FIG. 2 illustrates a preferred embodiment for the AC power circuit (7 inFIG. 1) of the present invention. In this embodiment, the AC powercircuit uses a triac 150 and optocoupler 140 to delay the onset of ACpower in the amplifier. This time delay power-on circuit delays theonset of AC power to allow the control circuit to stabilize and avoidloud pops when switched on.

In the circuit, AC power from an outside AC power source (e.g., walloutlet, generator, etc.) is provided through an electrical pole 101 andan electrical pole 103. Electrical poles 101 and 103 are coupledrespectively by an electrical connection 102 and an electricalconnection 104 in a parallel electrical circuit with a two-pole circuitbreaker 105. Electrical connection 102 is coupled from circuit breaker105 to a transformer 110 (e.g., 12-volt transformer). Electricalconnection 104 is also coupled from circuit breaker 105 to transformer110.

Transformer 110 steps down the supply voltage (e.g., from 120-volts ACto 12-volts AC). Current flows from transformer 110 through twoelectrical connections 111 and 113 to a bridge rectifier 112. The outputfrom bridge rectifier 112 passes through electrical connections 116 and114 to a filter network 115. In a specific preferred embodiment, filternetwork 115 comprises a 2200 μF capacitor 117, a 100 μF capacitor 118,and a 0.1 μF capacitor 119 coupled in parallel with bridge rectifier 112by electrical connections 116 and 114.

An electrical connection 121 couples a power supply regulator 120 toelectrical connection 116. In a specific preferred embodiment, powersupply regulator 120 is of the type comparable to a Motorola 78L12.Power supply regulator 120 is coupled to an electrical ground 108 by anelectrical connection 123. A capacitor 124 and a capacitor 126 arecoupled to power supply regulator 120 by an electrical connection 122.The two capacitors 124 and 126 are also coupled together by electricalconnection 114.

An electrical connection 127 couples a resistor 128 to a terminal V₁₂125. Terminal V₁₂ 125 represents a source of direct current (DC) powersupplied for the circuit. In the preferred embodiment disclosed, thevoltage supplied is for a 12-volt circuit. Also in the preferredembodiment disclosed, resistor 128 is a 68 K-ohm resistor. A resistor129 is coupled to electrical connection 127 by an electrical connection130 in a parallel electric circuit configuration.

As stated, terminal V₁₂ 125 is coupled to electrical connection 127, andthis electric terminal V₁₂ 125 provides a DC power source (e.g.,12-volt). Resistor 128 and resistor 129 are both coupled to the DC powersource. Resistor 128 is coupled in series with another resistor 131 byelectrical connection 133. In a specific preferred embodiment, resistor131 is a 68 K-ohm resistor. Resistor 129 is coupled in series with acapacitor 132 by an electrical connection 134. Resistor 131 is coupledto an electrical ground 108 by an electrical connection 136, andcapacitor 132 is coupled to an electrical ground 108 by an electricalconnection 137.

A comparator 135 is coupled to electrical connections 133 and 134. Thenon-inverting input to comparator 135 is coupled to electricalconnection 134 by an electrical connection 139. The inverting input ofcomparator 135 is coupled to electrical connection 133 by an electricalconnection 141. Comparator 135 compares the input voltages of the twoelectrical connections. If the voltage at electrical connection 139 isless than the voltage at electrical connection 141, the output ofcomparator 135 will be low, with the voltage at the output at anelectrical connection 142 at the lowest possible value (e.g., digitaloutput=0). If the voltage at electrical connection 139 is greater thanthe voltage at electrical connection 141, the output of comparator 135will be high, with the voltage at the output at electrical connection142 at its highest value (e.g., digital output=1).

An optocoupler 140 is comprised of a light emitting diode (LED) 171 anda phototransistor 172 inside a component case. Light emitting diode 171emits light when the digital output value from comparator 135 equals 1(e.g., the voltage at electrical connection 139 is greater than that atelectrical connection 141). An electrical connection 143 couples aresistor 144 to the LED 171. An electrical connection 146 couplesresistor 144 to ground 108. In a specific preferred embodiment, resistor144 is a 560 K-ohm resistor.

Phototransistor 172 has a light sensitive base region. When lightstrikes the photosensitive base of phototransistor 172, theemitter-to-collector resistance falls, allowing current to flow throughphototransistor 172. When the digital output value from comparator 135equals 1 (logic 1 state), LED 171 is illuminated. Light from LED 171charges the base of phototransistor 172, permitting current flow throughphototransistor 172. Thus, optocoupler 140 functions as a switchtriggered by the output of comparator 135.

An electrical connection 152 couples circuit breaker 105 and the ACpower to a capacitor 157, a triode alternating current switch (triac)150, and a resistor 145. Resistor 145 is coupled to optocoupler 140 byan electrical connection 147. An electrical connection 149 furthercouples electrical connection 147 to the gate of triac 150. Triac 150 iscoupled to a terminal L₂ 165 and optocoupler 140 by an electricalconnection 151. Capacitor 157 is coupled to a resistor 155 by anelectrical connection 156, and resistor 155 is further coupled toterminal L₂ 165 by an electrical connection 153. Terminal L₁ 160 iscoupled to transformer 110 and breaker 105 by electrical connection 107.

Optocoupler 140 isolates triac 150 from the control circuit. Whenphototransistor 172 is activated by LED 171, voltage applied to the gateof triac 150 causes current to flow through triac 150 and energizeterminal L₂ 165. Once the gate activates triac 150, AC power willcontinue to terminal L₂ 165 and L₁ 160 as long as the circuit remainsenergized. The optocoupler 140 and triac 150 combination will delaycircuit power-up until the control circuit stabilizes, avoiding pops andhiss from the audio output.

FIG. 3 illustrates a preferred embodiment of a bridge rectifier 205 (10in FIG. 1) and a voltage divider (resistors 210, 215, and theirelectrical interconnection, 15 in FIG. 1) of the present invention. Apair of terminals L₁ 160 and L₂ 165 are coupled to bridge rectifier 205by electrical connections 201 and 202 respectively. Two electricaloutput connections from bridge rectifier 205 couple to aresistor-capacitor (RC) filter and resistor voltage divider networkarrangement. An electrical connection 208 couples bridge rectifier 205to terminal V_(H) 240. Terminal V_(H) 240 represents a high voltageterminal connection. An electrical connection 207 couples bridgerectifier 205 to an electrical connection 221, and to an electricalconnection 206. Electrical connection 221 is coupled to ground 108. Anelectrical connection 209 couples bridge rectifier 205 to a capacitor230. In a specific preferred embodiment, capacitor 230 is a 1000 μFcapacitor. Electrical connection 206 couples capacitor 230 to electricalconnection 207. Electrical connection 209 is also coupled to electricalconnection 208.

A resistor 210 and a resistor 215 are connected in series to each otherand to capacitor 230 in a parallel circuit. An electrical connection 212couples resistor 210 to electrical connection 208. An electricalconnection 211 further couples resistor 210 to resistor 215. Electricalconnection 221 couples resistor 215 to ground 108.

An electrical connection 213 couples resistors 210 and 215 to thenon-inverting terminal of an operational amplifier 218 (op amp 218). Anelectrical connection 217 couples the output of op amp 218 to theinverting terminal input of op amp 218. Thus configured op amp 218performs as a voltage follower. An electrical connection 216 connectsthe output of op amp 218 (the voltage follower) to a terminal T₁ 250.The arrangement of the resistors 210 and 215 and the electricalconnections 213 and 211 between resistors 210 and 215 comprises aresistor voltage divider network. One or both of resistors 210 and 215may be variable, to accommodate adjustment of the power variance signal.

FIG. 4 illustrates a preferred embodiment of the circuit for thetriangular wave modulator (91 in FIG. 1) of the present invention.Although the preferred embodiment shown in FIG. 4 discloses a design foran analog circuit, the equivalent functionality may be achieved throughdigital circuitry, such as, for example, by use of digital signalprocessors.

As seen in FIG. 4, a terminal T₁ 250 is coupled to a first resistor 382by an electrical connection 301. Resistor 382 is subsequently coupled toa first voltage multiplier 310 (20 in FIG. 1), an integrated circuitchip with a voltage multiplier circuit, by an electrical connection 383to pin 1. Terminal T₁ 250 is coupled to a second resistor 381 byelectrical connection 301 through an electrical connection 303. Resistor381 is subsequently coupled to first voltage multiplier 310 by anelectrical connection 384 to pin 8. Pin 7 of voltage multiplier 310 iscoupled to a capacitor 305 (typically 0.1 μF) by an electricalconnection 308. Pin 2 of first voltage multiplier 310 is coupled toelectrical connection 308 by an electrical connection 309.

Capacitor 305 is coupled to ground 108 by an electrical connection 306.Terminal V_(G) 302 is coupled to electrical connection 308 by anelectrical connection 304. Terminal V_(G) 302 represents a virtualground for supplying a ground reference to single power supplyelectrical components. Pin 5 of first voltage multiplier 310 is coupledto a resistor 315 by an electrical connection 312, and resistor 315 iscoupled to a terminal V₁₂ 125 by an electrical connection 314. In aspecific preferred embodiment, resistor 315 is 60 K-ohm resistor. Pin 6of first voltage multiplier 310 is coupled to terminal V_(G) 302 byelectrical connection 377.

Pin 4 of first voltage multiplier 310 is coupled to the inverting inputof an op amp 320 by an electrical connection 311. A resistor 325 iscoupled to the inverting input of op amp 320 by an electrical connection317, which is coupled to electrical connection 311. An electricalconnection 321 couples an RMS terminal 330 to the pin 8 input of asecond voltage multiplier 340 (23 FIG. 1) through an electricalconnection 336. An electrical connection 324 couples resistor 325 to theoutput of op amp 320 through an electrical connection 327. An electricalconnection 326 couples a resistor 335 to electrical connection 324.

Electrical connection 336 couples resistor 335 to pin 8 of secondvoltage multiplier 340. This signal input is the square of the varianceof the input voltage to first voltage multiplier 310. The signal fromRMS terminal 330 is added to this signal. The second input is from atriangular wave generator through pin 1 of second voltage multiplier340. Pin 7 of second voltage multiplier 340 is coupled to an electricalconnection 351 by electrical connection 341. Pin 2 of second voltagemultiplier 340 is coupled to electrical connection 341 by an electricalconnection 343.

Pin 5 of second voltage multiplier 340 is coupled to a resistor 355 byan electrical connection 337. Resistor 355 is further coupled to aterminal V₁₂ 125 by an electrical connection 339. In a specificpreferred embodiment, resistor 355 is a 60 K-ohm resistor. Pin 6 ofsecond voltage multiplier 340 is connected to V_(G) 302 by an electricalconnection 379 which is coupled to electrical connection 351.

Pin 4 of second voltage multiplier 340 is the output of the two voltagemultipliers. This output is connected to an inverter amplifier circuit,comprising an op amp 350 and resistor 358. Pin 4 of second voltagemultiplier 340 is coupled to the inverting input of op amp 350 by anelectrical connection 344. Electrical connection 356 couples resistor358 to electrical connection 344. The output of op amp 350 is coupled toelectrical connection 357, which couples resistor 358 to capacitor 360by connection 352. Capacitor 360 is coupled to terminal T₃ 375 byelectrical connection 361.

Pin 1 of second voltage multiplier 340 receives the input triangularwave signal. Terminal T₂ 380 is coupled to a capacitor 365 by electricalconnection 366. In a specific preferred embodiment, capacitor 365 is a0.047 μF capacitor. Capacitor 365 is coupled to the non-inverting inputof a voltage follower op amp 370 by an electrical connection 371. Theoutput of op amp 370 is coupled to a resistor 345 by an electricalconnection 346. In a specific preferred embodiment, resistor 345 is a 10K-ohm resistor. Electrical connection 346 is coupled to the invertinginput of voltage follower op amp 370 by an electrical connection 373.Resistor 345 is coupled to pin 1 of second voltage multiplier 340 by anelectrical connection 342.

FIG. 5 illustrates a preferred embodiment of the present invention forthe pulse width modulation controller (93 in FIG. 1) including its audioinput circuitry, the triangular wave generator, and the pulse widthmodulation amplifier. The audio source signal input to the amplifier isthrough terminals T₄ 401 and T₅ 402. Terminal T₄ 401 is coupled to acapacitor 412 by an electrical connection 407. In a specific preferredembodiment, capacitor 412 is a 22 μF capacitor. A resistor 405 iscoupled to electrical connection 407 by an electrical connection 408. Ina specific preferred embodiment, resistor 405 is a 100 K-ohm resistor.Resistor 405 is coupled to a terminal V_(G) 302 by an electricalconnection 409, and terminal T₅ 402 is coupled to electrical connection409 by an electrical connection 404.

Capacitor 412 is coupled to a resistor 415 by an electrical connection406. In a specific preferred embodiment, resistor 415 is an 11 K-ohmresistor. A capacitor 410 is coupled to electrical connection 406 by anelectrical connection 403. In a specific preferred embodiment, capacitor410 is a 0.1 μF capacitor 410. Resistor 415 is coupled to thenon-inverting terminal of an op amp 416 by an electrical connection 414.Capacitor 410 is connected in a parallel circuit to resistor 415 by anelectrical connection 411 connected to electrical connection 414.

Op amp 416 is configured as a follower. Electrical connection 414 iscoupled to the non-inverting input of op amp 416. The output of the opamp 416 is coupled to a resistor 418 by an electrical connection 413. Ina specific preferred embodiment, resistor 418 is a 390-ohm resistor. Anelectrical connection 417 couples electrical connection 413 to theinverting input of op amp 416, thus configuring op amp 416 as a voltagefollower. Resistor 418 is coupled to a capacitor 420 by an electricalconnection 419. In a specific preferred embodiment, capacitor 420 is a22 μF capacitor. Capacitor 420 is coupled to a pulse width modulationcontroller 430 (93 in FIG. 1).

In the preferred embodiment disclosed, PWM controller 430 is anintegrated circuit chip, which provides the triangular wave generatorand internal comparator circuit. An electrical connection 421 isconnected to PIN 1 (AUDA) of PWM controller 430. A terminal AA 425 iscoupled to electrical connection 421 by an electrical connection 426.Terminal AA 425 represents the audio input to the circuit. In thepreferred embodiment, the audio input is buffered as shown by voltagefollower 416. A capacitor 423 is coupled to electrical connection 421 byan electrical connection 422, and the capacitor 423 is coupled to ground108 by an electrical connection 427. In a specific preferred embodiment,capacitor 423 is a 6800-pF capacitor.

An electrical connection 451 couples the audio input signal to aninverting amplifier 450. Electrical connection 451 is coupled to aresistor 452. An electrical connection 449 couples resistor 452 to theinverting input of op amp 450. An electrical connection 467 coupleselectrical connection 449 to another resistor 448. In a specificpreferred embodiment, resistor 452 and resistor 448 are 22 K-ohmresistors.

A capacitor 456 is coupled to electrical connection 451 by an electricalconnection 477. Capacitor 456 is coupled to ground 108 by an electricalconnection 457. In a specific preferred embodiment, capacitor 456 is a47-pF capacitor. A resistor 454 is coupled to electrical connection 477by an electrical connection 453, in a parallel circuit arrangement withcapacitor 456. An electrical connection 459 couples resistor 454 toconnection 458, thence to Terminal V_(G) 302.

Terminal V_(G) 302 is coupled to electrical connection 459 by anelectrical connection 458. An electrical connection 461 coupleselectrical connection 459 to the non-inverting input of op amp 450. Acapacitor 462 is coupled to electrical connection 461 by an electricalconnection 469, and electrical connection 493 couples capacitor 462 toelectrical connection 495 and ground 108.

The output of the op amp 450 is coupled to a resistor 445 by anelectrical connection 471. In a specific preferred embodiment, resistor445 is a 390-ohm resistor. Resistor 445 is coupled to a capacitor 443 byan electrical connection 444. In a specific preferred embodiment,capacitor 443 is a 22-μF capacitor. An electrical connection 479 couplescapacitor 443 to pin 8, the Audio B (AUD B) input, on controller 430. Anelectrical connection 481 couples electrical connection 479 to acapacitor 440, and electrical connection 497 couples capacitor 440 toground 108. In a specific preferred embodiment, capacitor 440 is a6800-pF capacitor 6800.

In a specific preferred embodiment, pulse width modulation controller430 is a Zetex ZXCD 1000, the internal configuration of which isillustrated in FIG. 9. In this embodiment, electrical connection 421 iscoupled to pin 1 of PWM controller 430. Pin 1 is the Audio A (AUD A)input, which is the non-inverting input to the first internal comparatoron controller 430. The Audio B (AUD B) input, pin 8, is coupled to opamp 450 by electrical connection 479. AUD B is the non-inverting inputto the second internal comparator on controller 430. A terminal T₃ 375,the output from second voltage multiplier 340, is coupled to theTriangle B (TRI B) input, pin 7, of PWM controller 430 by electricalconnection 489. Electrical connection 429 couples electrical connection489, and terminal T₃ 375, to Triangle A (TRI A) input, pin 2 of PWMcontroller 430.

PWM controller 430 includes two internal comparators (see FIG. 9). TheAUD A input, pin 1 of PWM controller 430, is coupled to thenon-inverting input of the first internal comparator, and the TRI Ainput, pin 2 of PWM controller 430, is the inverting input of the firstinternal comparator. The Output A (OUT A), pin 15 of PWM controller 430,is the output signal from the first internal comparator and is coupledto terminal T₆ 498 by an electrical connection 463. The AUD B input, pin8 on PWM controller 430, is the non-inverting input of the secondinternal comparator, and the TRI B input, pin 7 of PWM controller 430,is the inverting input of the second internal comparator. The Output B(OUT B), pin 10 of PWM controller 430, is the output signal from thesecond internal comparator and is coupled to terminal T₇ 499 by anelectrical connection 486.

PWM controller 430 also generates the triangular wave signal input tosecond voltage multiplier 340. OSC A generates a triangular wave signal.The OSC A output, pin 3, is coupled to terminal T₂ 380 by electricalconnection 431. Referring back to FIG. 4, it is seen that the triangularwave signal at terminal T₂ 380 subsequently passes through capacitor365, follower 370, and resistor 345, to the pin 1 input of secondvoltage multiplier 340. Referring again to FIG. 5, pin 5 of PWMcontroller 430, COSC, is coupled to a capacitor 437 by electricalconnection 432, and capacitor 437 is coupled to ground 108 by electricalconnection 439. In a specific preferred embodiment, capacitor 437 is a330-μF capacitor. Pin 9 of PWM controller 430, GND, is coupled to ground108 by electrical connection 479. Pin 11 of PWM controller 430, GND2, iscoupled to electrical connection 479 and ground 108 by an electricalconnection 496.

Pin 12 of PWM controller 430, 9VB, is connected to an internal powersupply of PWM controller 430 (typically 9-volt), and is coupled by anelectrical connection 472 to three capacitors 470, 474, and 480, whichare individually connected in a bridge, or parallel arrangement toelectrical connection 479. Pin 14 of the PWM controller 430, 9VA, isconnected to the internal power supply of PWM controller 430 (typically9-volt), and is coupled by an electrical connection 469 to electricalconnection 472 and the three capacitors 470, 474, and 480. Pin 16 of thePWM controller 430, 5V5, is connected to an internal power supply of PWMcontroller 430 (typically 5.5-volt), and is coupled to a capacitor 435by an electrical connection 461. Capacitor 435 is coupled to ground 108by an electrical connection 443. An electrical connection 439 couples acapacitor 434 to electrical connection 461 and to 5V5. An electricalconnection 441 couples capacitor 434 to ground 108.

Pin 13, V_(cc), receives the external power supply to PWM controller430. Pin 13, V_(CC) is coupled to the power supply terminal V₁₂ 125(12-volt in the specific preferred embodiment), by electrical connection468, and is coupled by three capacitors 473, 475, and 478 in a bridge,or parallel circuit arrangement, to electrical connection 479 and ground108. The external power supply V_(CC) supplies power to PWM controller430, and regulators on PWM controller 430 drop the power to the internalpower sources (typically 9-volt and 5.5-volt) required by the internalcircuitry of PWM controller 430.

FIG. 6 illustrates a preferred embodiment for the power devicetransistor and filter (30 in FIG. 1) of the present invention. Aterminal T₆ 498 is coupled by an electrical connection 501 to anelectrical connection 503. Electrical connection 503 couples a capacitor521 to a capacitor 505 in series. An electrical connection 527 couplescapacitor 521 to the anode of diode 530. An electrical connection 529couples the cathode of diode 530 to a terminal V_(H) 213. An electricalconnection 533 couples a resistor 534 to electrical connection 529 andto the cathode of diode 530 in a parallel circuit. An electricalconnection 531 couples electrical connection 527 and an electricalconnection 532 to resistor 536. An electrical connection 535 coupleselectrical connection 531 to the anode of a diode 537 in a parallelcircuit to a resistor 536. Cathode of diode 537 is coupled to electricalconnection 539 by an electrical connection 538.

An electrical connection 545 couples a capacitor 546 to electricalconnection 529 and terminal V_(H) 213 and the cathode of diode 530. In aspecific preferred embodiment, capacitor 546 is a 0.47-μF capacitor. Anelectrical connection 548 couples capacitor 546 to ground 108.

Electrical connection 539 couples resistor 536 and electrical connection538 to the gate of a P-channel metal-oxide-semi-conductor field-effecttransistor (MOSFET) 540. The source of MOSFET 540 is coupled toelectrical connection 529 by an electrical connection 541. The drain ofMOSFET 540 is connected to an electrical connection 520 by an electricalconnection 542.

Capacitor 505 is coupled to the cathode of a diode 510 by an electricalconnection 504. An electrical connection 508 couples electricalconnection 504 to a resistor 513. An electrical connection 502 coupleselectrical connection 508 to a resistor 511 in a parallel circuit todiode 510. An electrical connection 509 couples resistor 511 to anelectrical connection 507. An electrical connection 512 couples thecathode of a diode 514 to electrical connection 502 in a parallelcircuit to resistor 513. An electrical connection 515 couples the anodeof diode 514 to an electrical connection 516, which is coupled toresistor 513.

Electrical connection 516 couples resistor 513 and the anode of diode514 to the gate of an N-channel MOSFET 517. The source of MOSFET 517 iscoupled to electrical connection 507 by electrical connection 519, andelectrical connection 519 is coupled to electrical connection 548 andground 108 by electrical connection 507. The drain of MOSFET 517 iscoupled to electrical connection 520 by an electrical connection 518.Electrical connection 520 is coupled to a inductor 543. Inductor 543 iscoupled to the first output terminal OUT₁ 601 of the amplifier by anelectrical connection 544. In a specific preferred embodiment, inductor543 is a 20-μH inductor. Electrical connection 528 couples a capacitor547 to electrical connection 520 and inductor 543. An electricalconnection 549 couples capacitor 547 to ground 108. In a specificpreferred embodiment, capacitor 547 is a 1-μF capacitor. The combinationof inductor 543 and capacitor 547 forms an LC filter configuration forthe signal output at OUT₁ 601.

A terminal T₉ 499 is coupled by an electrical connection 551 to anelectrical connection 553. Electrical connection 553 couples a capacitor571 and a capacitor 555 together in series. An electrical connection 577couples capacitor 571 to the anode of a diode 580. An electricalconnection 579 couples the cathode of diode 580 to a terminal V_(H) 214.An electrical connection 583 couples a resistor 584 to an electricalconnection 579 and the cathode of diode 580 in a parallel circuit. Anelectrical connection 581 also couples electrical connection 577 and anelectrical connection 582 to a resistor 586. An electrical connection585 couples electrical connection 581 to the anode of a diode 587 in aparallel circuit to resistor 586. The cathode of diode 587 is coupled toan electrical connection 589 by an electrical connection 588.

An electrical connection 595 couples a capacitor 596 to electricalconnection 579 and terminal V_(H) 214 and the cathode of diode 580. In aspecific preferred embodiment, capacitor 596 is a 0.47-μF capacitor.Electrical connection 598 couples capacitor 596 to ground 108.

An electrical connection 589 couples resistor 586 and an electricalconnection 588 to the gate of a P-channel MOSFET 590. The source ofMOSFET 590 is coupled to an electrical connection 579 by an electricalconnection 591. The drain of MOSFET 590 is connected to an electricalconnection 570 by an electrical connection 592.

Capacitor 555 is coupled to the cathode of a diode 560 by an electricalconnection 554. An electrical connection 558 couples electricalconnection 554 to a resistor 563. An electrical connection 552 coupleselectrical connection 558 to a resistor 561 in a parallel circuit todiode 560. An electrical connection 559 couples resistor 561 to anelectrical connection 557. An electrical connection 562 couples thecathode of a diode 564 to electrical connection 552 in a parallelcircuit to resistor 563. An electrical connection 565 couples the anodeof diode 564 to an electrical connection 566, which is coupled toresistor 563.

Electrical connection 566 couples resistor 563 and the anode of diode514 to the gate of an N-channel MOSFET 567. The source of MOSFET 567 iscoupled to electrical connection 557 by an electrical connection 569,and electrical connection 569 is coupled to an electrical connection 598and ground 108 by electrical connection 557. The drain of MOSFET 567 iscoupled to electrical connection 570 by an electrical connection 568.Electrical connection 570 is coupled to an inductor 593. Inductor 593 iscoupled to the second output terminal OUT₂ 602 of the amplifier by anelectrical connection 594. In a specific preferred embodiment, inductor593 is a 20-μH inductor. An electrical connection 578 couples acapacitor 597 to electrical connection 570 and inductor 593. Electricalconnection 599 couples capacitor 597 to ground 108. In a specificpreferred embodiment, capacitor 597 is a 1-μF capacitor. The combinationof inductor 593 and capacitor 597 forms an LC filter configuration forthe signal output at OUT₂ 602. A load device (not shown), typically aspeaker in audio applications, is connected to each of the outputs OUT₁601 and OUT₂ 602.

FIG. 7 illustrates an alternative preferred embodiment in which adynamic range compression component is added to the circuit. In thisembodiment, an RMS-to-DC converter integrated circuit 605 (RMS converter605) provides modulation to compensate for volume changes in the inputsignal (e.g., dynamic range compression). The triangular wave, inaddition to being modulated to compensate for power variances, isfurther modulated with the output of the RMS (root-mean-square)converter 605. The RMS converter 605 generates a signal relative to theRMS value of the audio input at AA 425 to obtain variable compression ofthe audio level. In a specific preferred embodiment, RMS converter 605is an Analog Devices AD 736 RMS-to-DC converter integrated circuit. Pin1 of RMS converter 605 is coupled to a capacitor 610 by an electricalconnection 609. In a specific preferred embodiment, capacitor 610 is a10-μF capacitor. Electrical connection 641 couples a terminal V_(G) 302to capacitor 610. An electrical connection 608 couples pin 8 of RMSconverter 605 to electrical connection 641 and terminal V_(G) 302. Pin 2of RMS converter 605 is coupled to terminal AA 425 by an electricalconnection 603 and is the input into RMS converter 605.

Pin 3 of RMS converter 605 is coupled to a capacitor 625 by anelectrical connection 604. In a specific preferred embodiment, capacitor625 is a 47-μF capacitor. The output of RMS converter 605 at pin 6 iscoupled to a potentiometer 650 by electrical connection 616.Potentiometer 650 permits selectable, adjustable compression of thetriangular wave modulated circuit. The wiper leading from potentiometer650 is coupled to a resistor 645. Resistor 645 is coupled to an RMSterminal 330 by an electrical connection 647. In a specific preferredembodiment, resistor 645 is a 10 K-ohm resistor. An electricalconnection 652 couples potentiometer 650 to a terminal V_(G) 302.Electrical connection 616 from the output pin 6 of converter 605 iscoupled to capacitor 625 by electrical connection 617.

Pin 4 of converter 605 is coupled to an electrical ground 108 by anelectrical connection 607. An electrical connection 613 couples acapacitor 615 to electrical connection 607. In a specific preferredembodiment, capacitor 615 is a 0.1-μF capacitor. An electricalconnection 616 couples capacitor 615 to a terminal V_(G) 302. Anelectrical connection 611 couples electrical connection 607 to acapacitor 620, and electrical connection 612 couples capacitor 620 topin 5 of the converter 605. In a specific preferred embodiment,capacitor 620 is a 100-μF capacitor.

Pin 7 of converter 605 is coupled to a terminal V₁₂ 125 by an electricalconnection 618. An electrical connection 639 couples electricalconnection 641, and terminal V_(G) 302, to a capacitor 640. Anelectrical connection 634 couples capacitor 640 to electrical connection618 and the terminal V₁₂ 125. In a specific preferred embodiment,capacitor 640 is a 0.1-μF capacitor.

FIG. 8 illustrates the connectivity between the various circuitcomponents described in detail hereinabove, showing the relationshipbetween the rectifier and divider circuit of FIG. 3, the triangle wavemodulator of FIG. 4, the pulse width modulator of FIG. 5, and the powerdevice of FIG. 6, as might be implemented in a production circuit board.

FIG. 9 illustrates the internal operative connectivity for pulse widthmodulation controller 430 described in the preferred embodiment indetail in connection with FIG. 5.

OPERATION OF THE PREFERRED EMBODIMENTS

FIG. 10 illustrates in schematic, block diagram form, the modulatedtriangular wave amplifier as similarly illustrated in FIG. 1, accordingto a preferred embodiment of the present invention. In FIG. 10, thedevice is configured as a noise-canceling amplifier, which is capable ofremoving or canceling “ripple” from a power supply. Power is supplied torectifier 10. A signal (such as an audio signal) to be amplified may beprovided to an optional pre-amplifier 1011 to boost the signal strength.The amplified signal is then input to PWM controller 93, while rectifiedpower (DC) is input to TWM 91.

A triangle (Δ) wave generated by triangle wave generator 91 (27 in FIG.1, and described in detail in connection with FIG. 4) is coupled fromPWM controller 93 and is modulated by TWM 91 and returned to PWMcontroller 93. The output of PWM controller 93 is input to power device30, which also receives rectified power from rectifier 10. Thus, theoutput of PWM controller 93 is employed to cancel noise present in therectified power signal. The output of power device 30 is typicallyapplied to a filter 40 and then to a load 45, such as an audio speaker.

FIG. 11 illustrates in schematic, block diagram form the modulatedtriangular wave amplifier according to another preferred embodiment ofthe present invention. In this preferred embodiment, the device isconfigured to modify the dynamic range of an input signal (i.e., tolimit or enhance bandwidth, equalize the signal, or to compensate for,or cancel, signal elements). In this embodiment, power is supplied torectifier 10, while a signal (such as an audio signal) to be modifiedmay be provided to an optional pre-amplifier 1011 to boost the signalstrength. Rectified power (DC) is input to TWM 91. The amplified signalis input to a Signal Processor 1013 coupled between the output ofpre-amplifier 1011 and TWM 91. The amplified signal is also input,without signal processing, to PWM controller 93.

The choice of signal processor 1013 “type” corresponds with the desiredmodification to the signal. Thus, the output of PWM controller 93, withthe addition of signal processing through TWM 91, is used in powerdevice 30 to accomplish the desired modification to the input signal,while power-supply noise-cancellation is also achieved. Thisconfiguration is most effectively adapted for audio input signals withan audio speaker load 45.

FIG. 12 illustrates in schematic block diagram form, the triangular wavemodulated amplifier, according to another preferred embodiment of thepresent invention. In this preferred embodiment, the device isconfigured to introduce an overlay or cancellation signal (pink noise,an advertisement, compensation for ambient noise, etc.) onto the outputsignal to load 45.

The overall configuration is identical to that in FIG. 11, with anadditional signal source 1015 supplied to signal processor 1013. Thesignal processor 1013 then supplies the processed signal to TWM 91,which in turn affects the desired modification to the output signal ofPWM controller 93. By this configuration, an overlay or background noisecompensation signal may be added while power supply noise-cancellationis also provided.

In each of the embodiments of the present invention disclosed in FIG.10, FIG. 11, and FIG. 12, it is understood that unregulated DC power maybe supplied directly TWM 91, if DC power, rather than AC power, is theavailable power source.

While the invention has been particularly shown and described withrespect to preferred embodiments, it will be readily understood thatminor changes in the details of the invention may be made withoutdeparting from the spirit of the invention.

I claim:
 1. A power amplifying device processing an input alternatingcurrent power signal comprising: a rectifier that produces a directcurrent power signal from the input alternating current power supplysignal; a first voltage multiplier receiving a first input signal and asecond input signal derived from voltage division of the direct currentpower signal, and producing a first output signal; a second voltagemultiplier receiving a third input signal from the first output signaland a fourth input signal, and producing a second output signal; a pulsewidth modulation controller receiving a fifth input signal from thesecond output signal and a sixth input signal from an audio inputsignal, and producing a third output triangular wave signal as thefourth input signal, and producing a fourth output signal; and, whereasthe power amplifying device produces an output power signal based on thefourth output signal and the direct current power signal.